P-glu-his-trp-ser-tyr-d-lys-leu-arg-pro-gly-nh&#39; 2 &#39;and intermediates

ABSTRACT

D-Lys6-LRF, is described as well as its synthesis by solid phase techniques and novel intermediates formed by such synthesis. This novel decapeptide stimulates the release of luteinizing hormone and is useful in mammals in increasing and regulating fertility.

United States Patent McKinely et al.

[4 5] July 22, 1975 P-GLU-H1S-TRP-SER-TYR-D-LYS-LEU-ARG- PRO-GLY-NH AND INTERMEDIATES Inventors: Wayne A. McKinely, Wallingford;

Dimitrois Sarantakis, West Chester, both of Pa.

American Home Products Corporation, New York. NY.

Filed: May 22, 1974 Appl. No.: 472,269

Assignee:

11.8. C1 260/112.5; 424/177 Int. Cl... C07c 103/52; C07g 7/00; A6lk 37/00 Field of Search 260/78 A, 112.5; 424/177 References Cited OTHER PUBLICATIONS Chang et al.: J. Med. Chem., 15, 623-627, (1972).

Fujino et al.: Biochem. Biophys. Res. Comm., 57, 12484256, (1974).

Primary Examiner-Lewis Gotts Assistant Examiner-Reginald J. Suyat ity.

5 Claims, No Drawings P-GLU-HlS-TRP-SER-TYR-D-LYS-LEU-ARG-PRO- GLY-NH AND INTERMEDIATES This invention relates to the novel decapeptide p- Glu-His-Trp-Ser-Tyr-D-Lys-Leu-Arg-Pro-Gly-NH its process of manufacture and novel intermediates formed in such synthesis.

The luteinizing hormone releasing factor (hereafter called LRF) is the decapeptide, L-(5-oxoprolyl)-L- histidyl-L-tryptophyl-L-seryl-L-tyrosyl-glycyl-L-leucyl- L-arginyl-L-prolyl-glycine amide. See Matsuo et al., Biochem. & Biophy. Res. Comm. 46, pp. 1334-1339 (197l). This decapeptide is secreted by the hypothalamus and carried to the adenohypophysis where it stimulates the release of the luteinizing hormone and the follicle stimulating hormone. The present invention concerns itself with structural modifications of LRF in which the glycine in the six position of the peptide chain has been replaced by D-lysine. Monahan et al., Biochem. 12, pp 4616-4620 (November 1973) describe D-Ala -LRF as stimulating the release of luteinizing hormone.

The novel peptides of the present invention are represented by the compounds of the formula:

p-Glu-l-lis-Trp-Ser-Tyr-D-Lys-Leu-Arg-Pro-Gly- NH2(l) and its non-toxic acid addition salts. All chiral amino acid residues identified in formula I supra, and the other formulas hereinafter are of the natural or L-configuration unless specified otherwise.

Also contemplated within the scope of the present invention are intermediates wherein:

N" means the side chain nitrogen atoms of arginine;

N means the nitrogen atoms of the imidazole ring of histidine;

R is a protecting group for the N 5 N and N u nitrogen atoms of arginine selected from the group consisting of nitro, tosyl, benzyloxycarbonyl, adamantyloxycarbonyl; and tert-butyloxycarbonyl; or R is hydrogen which means there are no protecting groups on the side chain nitrogen atoms of arginine. Where the protecting group is nitro or tosyl, the protection is on either one of the N w N nitrogens and in the case of benzyloxycarbonyl, or adamantyloxycarbonyl, the protection is on the N 3 nitrogen and either one of the N N nitrogen atoms;

R is a protecting group for the side chain amino substituent of lysine or R is hydrogen which means there is no protecting group on the side chain amino substituent. Illustrative of suitable side chain amino protecting groups are chlorobenzyloxycarbonyl, benzyloxycarbonyl, tosyl, tamyloxycarbonyl, t-butyloxycarbonyl, etc. The selection of such a side chain amino protecting group is not critical except that it must be one which is not removed during cleavage of the a-amino protecting group during the synthesis until the peptide of the desired amino acid sequence is obtained. Hence, the a-amino protecting and side chain amino protecting group cannot be the same;

R is a protecting group for the phenolic hydroxyl group of tyrosine selected from the group consist- LII ing of tetrahydropyranyl, tert-butyl,'trityl-,--benzyl,

tecting group is 2,6-.dichlorobenzyl or benzyl; or R is hydrogen which means there is no protecting groupon the phenolic hydroxy function;

R is a protecting group for the alcoholic hydroxyl group of serine and is selected from the group consisting of acetyl, benzoyl, tetrahydropyranyl, tertbutyl, trityl, benzyl, 2,6-dichlorobenzyl or R is hydrogen which means there is no protecting group on the alcoholic oxygen atom. Preferably R is benzyl;

R is preferably hydrogen but may also be an a-amino protecting group. The a-amino protecting group contemplated by R are those known to be useful in the art in the step-wise synthesis of polypeptides. Among the classes of a-amino protecting groups covered by R are (l) acyl type protecting groups illustrated by the following: formyl, trifluoroacetyl,

toluenesulfonyl (tosyl), nitrophenylsulfenyl, etc.;

(2) aromatic urethan type protecting groups illustrated by benzyloxycarbonyl and substituted benzyloxycarbonyl such as p-chlorobenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl; (3) aliphatic urethan protecting groups illustrated by tertbutyloxycarbonyl, diisopropylmethoxycarbonyl, isopropyloxycarbonyl, allyloxycarbonyl; (4) cycloalkyl urethan type protecting groups illustrated by cyclopentyloxycarbonyl, adamantyloxycarbonyl, cyclohexyloxycarbonyl; and d-isobornyloxycarbonyl; (5) thio urethan type protecting groups such as phenylthiocarbonyl; (6) alkyl type protecting groups as illustrated by triphenylmethyl (trityl), benzyl; (7) trialkylsilane groups such as trimethylsilane. The preferred oz-amino protecting group defined by R are selected from the class consisting of benzyloxycarbonyl, tert-butyloxycarbonyl, tertamyloxycarbonyl and d-isobornyloxycarbonyl;

R is a protecting group for the imidazole nitrogen atom selected from the group consisting of tosyl, benzyl, trityl, 2,2,2-trifluoro-1-benzyloxycarbonylaminoethyl and 2,- 2,2-trifluorol -tert-butyloxycarbonylaminoethyl or 2,4-dinitrothiophenyl.

ln formula II at least one of R, R R, R or R is a protecting group.

X is selected from the group consisting of NH OH, O-(lower)alkyl in which (lower)alkyl is C, through C (e.g. methyl, ethyl, pentyl, isopropyl, hexyl, etc.), 0- benzyl and an anchoring bond used in solid phase peptide synthesis linked to a solid polystyrene resin support represented by one of the formulas:

and

styrene resin support The polystyrene resin support is preferablya copolymer of styrene with about I to 2% divinyl benzene as a cross linking agent which causes the polystyrene polymer to be completely insoluble in most organic sol vents. The polystyrene polymer is composed of long alkyl chains bearing a phenyl ring on every second carbon and the terminal amino acid residue (Gly) is joined through a covalent carbon to nitrogen or oxygen bond to these phenyl rings. The alkyl chains are cross linked at approximately every fiftieth carbon by p-substituted phenyl residues derived from divinyl benzene. In formula (III) the symbol (1: means phenyl.

In selecting a particular side chain protecting group to be used in the synthesis of the peptides of formula (I), the following rules should be followed: (a) the protecting group must be stable to the reagent and under reaction conditions selected for removing the a-amino protecting group at each step of the synthesis, (b) the protecting group must retain its protecting properties, (i.e., not be split off under coupling conditions), and (c) the side chain protecting group must be removable upon the completion of the synthesis containing the desired amino acid sequence under reaction conditions that will not alter the peptide chain.

Illustrative of pharmaceutically acceptable, nontoxic salts of formula I are hydrochloride, hydrobromide, sulfate, phosphate, maleate, acetate, citrate, benzoate, succinate, malate, ascorbate, and the like.

The decapeptides of formulas (I) and (II) are prepared using solid phase synthesis. The synthesis is commenced from the C-terminal end of the peptide using an a-amino protected resin. Such a starting material can be prepared by attaching an a-amino protected glycine to a benzhydrylamine resin, a chloromethylated resin or a hydroxymethyl resin, the former being preferred. The preparation of benzhydrylamine resin is described by P. Rivaille et al., Helv. 54, 2772 (l97l) and the preparation of the hydroxymethyl resin is described by Bodanszky et al., Chem. Ind. (London) 38, 1597-98 (1966). A chloromethylated resin is commercially available from Bio Rad Laboratories Richmond, California and the preparation of such a resin is described by Stewart et al., Solid Phase Peptide Synthesis (Freeman & Co. San Francisco 1969), Chapter 1, pp 1-6. In using the benzhydrylamine resin an amide anchoring bond is formed with the a-amino protected glycine as follows:

cleavage of the peptide from the resin support must be converted to the C-terminal amide. The preferred procedure is to ammonalyse the protected peptide off the resin and them remove the protecting group by hydrogenolysis or by hydrogen fluoride cleavage. An alternate procedure would be to cleave by transesterification with methanol/(Et) N and then convert the resulting ester into an amide and subsequently deprotect as described above. See J. M. Stewart Solid Phase Peptide Synthesis, pp 42-46 (Freeman & Co. San Francisco 1969).

The oz-amino protected glycine is coupled to the benzhydrylamine resin with the aid of a carboxyl group activating compound such as diisopropylcarbodiimide. Following the coupling of the a-amino protected glycine to the resin support, the oz-amino protecting group is removed such as by using trifluoroacetic acid in dichloromethane, trifluoroacetic acid alone or I-ICI in dioxane. The deprotection is carried out at a temperature between about 0C and room temperature. Other standard cleaving reagents and conditions for removal of specific a-amino protecting groups may be used as described in Schroder & Lubke, The Peptides, I 7275 (Academic Press 1965). After removal of the a-amino protecting group the remaining a-amino protected amino acids are coupled step-wise in the desired order to obtain a compound of formula (I). However, as an alternate to adding each amino acid separately to the reaction, some of them may be coupled prior to addition to the solid phase reactor. Each protected amino acid or amino acid sequence, is introduced into the solid phase reactor in about a four-fold excess and the coupling is carried out in a medium of dimethylformamide: dichloromethane (1:1) or in dimethylformamide or dichloromethane alone. In cases where incomplete coupling occurs the coupling procedure is repeated before removal of the a-amino protecting group, prior to the coupling of the next amino acid to the solid phase reactor. The success of the coupling reaction at each stage of the synthesis is monitored by the ninhydrin reaction as described by E. Kaiser et al., Analyt. Biochem, 34, 595 (1970).

After the desired amino acid sequence has been synthesized, the peptide is removed from the resin support by treatment with a reagent such as hydrogen fluoride which not only cleaves the peptide from the resin but also cleaves all remaining side chain protecting groups and the a-amino protecting group (if present) on pyroglumatic acid to obtain directly a compound of formula I in the case where the benzhydrylamine resin was used. Where a chloromethylated resin is used the peptide may be separated from the resin by methanolysis after which the recovered product is chromatographed on silica gel and the collected fraction subject to ammonalysis to convert the methyl ester to the C-terminal amide. Any side chain protecting group may then be cleaved as previously described or by other procedures such as catalytic reduction (e.g. Pd on C) using conditions which will keep the Trp moiety intact. When using hydrogen fluoride for cleaving, anisole is included in the reaction vessel to prevent the oxidation of labile amino acid (e.g. tryptophan).

The solid phase synthesis procedure discussed supra is well known in the art and has been essentially described by M. Monahan et al., C. R. Acad. Sci. Paris, 273, 508 (197]).

The nomenclature used for peptides is describedby Schroder & Lubke, supra, pp viii-xxix and in Biochemistry 11, 1726-1732 (1972).

The following examples are illustrative of the preparation of the compounds of formulas l and 11. 5

EXAMPLE 1 L-Pyroglutamyl-N -tosyl-L-histidyl-L-tryptophyl-O- benzyl-L-seryl- O-2,6-dichlorobenzyl-L-tyrosyl-N -2- chlorobenzyloxycarbonyl-D- lysyl-L-leucyl-N"-tosyl-L-arginyl-L-prolyl-glycy1 benzhydrylamine resin Benzhydrylamine hydrochloride resin (3 g) in a Merrifield vessel is treated with trifluoroacetic acid (two times, for 5 minutes each), washed with methylene chloride (two times) and dimethylformamide (two times), neutralized with 15% triethylamine in dimethylformamide (two times, for minutes each), and washed with methylene chloride (four times), methanol (three times), and methylene chloride, again (three times). A solution of t-Boc-glycine (0.79 g, 4.5 m moles) im methylene chloride and dimethylformamide (10:1) is added to the vessel and shaken for minutes. Diisopropylcarbodiimide (0.72 ml, 4.5 m moles) is added next, and the mixture shaken at ambient temperature for 5 hours. The reaction mixture is filtered, washed with methylene chloride, and the vessel recharged in the above manner with t-Boc-glycine and diisopropylcarbodiimide. Twenty hours later, the reaction mixture is filtered, washed with methylene chloride, dimethylformamide, 15% triethylamine in dimethylformamide, dimethylformamide, methylene chloride (three times), methanol (two times), and methylene chloride (three times), and a sample is dried in vacuo. The resin is found to be substituted to the extent of 0.30 m moles of t-Boc-glycine per gram of resin. 0

The following amino acid residues are introduced onto the above resin consecutively: t-Boc-L-proline (4.5 m moles), t-Boc-N-tosyl-L-arginine (2.3 m moles) and t-Boc-L-leucine (2.3 m moles). The remainder of the synthesis is carried out using a Beckman 990 peptide synthesizer adding the following residues: t-Boc-N -2-ch1orobenzyloxycarbonyl-D-lysine (4.5 m moles), t-Boc-O-2,6-dich1orobenzyl-L-tyrosine (4.5 m moles), t-Boc-O-benzyl-L-serine (4.5 m moles), t-Boc-L-tryptophan (4.5 m moles), t-Boc-N -tosyl-L- 5O histidine, (4.5 m moles), and L-pyroglutamic acid (4.5 m moles). All the couplings are carried out in a mixture of methylene chloride and dimethylformamide (3:1) at ambient temperature using a 10% excess of diisopropylcarbodiimide, which is added in two portions over a period of 30 minutes. A coupling time of 18 hours is used for the additions done manually with the Merrifield vessel and a time of 2 hours is usedwith the automated synthesizer. Each coupling is then effected a second time using one half the original quantities of reactants and allowing a reaction time of 2 hours. The washings between couplings are the same as those described above after the coupling of t-Boc-glycine. The deprotection and neutralization is carried out as follows: (a) 1:1 methylene chloride and trifluoroacetic 5 acid containing 5% ethanedithiol (for a total time of 30 minutes); (b) methylene chloride; (c) dimethylformamide; (d) 15% triethylamine in dimethylformamide (two times for 10 minutes each); (e) dimethylformamide (two times); (f) methylene chloride (six times).

The washed resin is dried in vacuo overnight.

EXAMPLE 2 L-Pyroglutamyl-L-histidyl-L-tryptophyl-L-seryl-L- tyrosyl-D-lysyl- L-leucyl-L-arginyl-L-prolyl-glycinamide The above described preparation obtained in Example 1 is treated in vacuo with anhydrous liquid hydrogen fluoride ml) and anisole (10 ml) at ambient temperature for 40 minutes. The hydrogen fluoride is removed as quickly as possible under reduced pressure, and the residue extracted with ether. The remaining residue is extracted with 0.5 N acetic acid and lyophylized to leave the above titled product (1.44 g).

EXAMPLE 3 Purification and characterization of L-pyroglutamyl-L-histidyl-L- tryptophyl-L-seryl-L-tryosyl-D-lysyl-L-1eucyl-L arginyl-L-prolylglycinamide The above titled crude product obtained in Example 2 is purified as follows: 1.44 g of this product in 5 ml of the upper phase of a 1:1 mixture of n-butanol and 0.1 M ammonium acetate is applied to the top of a column (2.9 cm in diameter and cm in height) with a bed of Sephadex G-25 F previously equilibrated with the upper phase of that system. The column is eluted with the upper phase and fractions of 4 ml each are taken. The column effluis monitored by use of the F0- lin-Lowry color reaction on every third fraction. Five peptide containing fractions are obtained, but they contain only 13% of the material applied to the column. Elution of the column with 0.5 N acetic acid produces three main peptide containing fractions: 1) 222 mg, 11) 621 mg, 111) 145 mg. Amino acid analysis and thin layer chromatography system BWAP (4:2:1 :1) (nbutanolzwater acetic acid pyridine) show fractions 11 and I11 (766 mg) to contain the same major material. They are combined and applied in 3 ml of 0.5 N acetic acid to a column (2.9 cm in diameter and 100 cm in height) with a bed of Sephadex G-15 previously equilibrated with 0.5 N acetic acid, and eluted with that solvent. Fractions of 2 ml each are taken and monitored as described before. Five major fractions are obtained: (A) 117-115 (101 mg), (B) 116-125 (100 g), (C) 126-133 (22 mg), (D) -145 (30 mg) (E) 146-155 (221 mg). Fraction B is homogenous by thin layer chromatography system BWAP (4:2:1:1) on silica gel (R, 0.37). Thin layer chromatograms are visualized by chlorine peptide reagent; [0:]D 36.65 (c 1.00%, 1% AcOH).

After hydrolysis of the peptide in 6 N l-lCl containing 4% thioglycolic acid for 20 hours at 1 10C in a closed system under nitrogen, the following values for the amino acid residues are obtained: Glu 0.97; His 0.92, Trp 0.73; Ser 0.78; Tyr 1.04; Lys 1.05; Leu 0.97; Arg 0.85; Pro 1.02; Gly 1.00.

The compound of Example 3 was tested in vitro for its ability to increase the release of luteinizing hormone (Ll-l). These tests are performed in rat tissue cultures, using the procedure described in Grant et al., Biochemical and Biophysical Research Communications, 51 pp 100-106 (1973) and the amount of hormone released 2,6-dichlorobenzyl, p-bromobenzyloxycarbonyl is determined by radioimmunoassay in accordance with and benzyloxycarbonyl or R is hydrogen;

the method described by Berson et al., Metabolism, 13, R is a protecting group for the alcoholic hydroxyl 1135 (1964). The compound of Example 3 was found group of serine and is selected from the group conto stimulate LH release at a concentration between 100 5 sisting of acetyl, benzoyl, tetrahydropyranyl, tertand picogram/ml. butyl, trityl, 2,6-dichlorobenzyl and benzyl or R is The biological activity of the compound of Example h d 3 was determined in vivo by the stimulation of release R i l ted from the group consisting of hydrogen of LH in ovariectomized rats pretreated with estrogen or an a amino protecting group;

and Progesterone Schally, Nail', 10 R is a protecting group selected from the group con- Reddlng and Arimura, 1 Biol- Chem- 7230 sisting of tosyl, benzyl, trityl, 2,4-dinitrothiophenyl, 2,- )l P y {Milo-immunoassay for rat LH as 2,2-trifluoro-1-benzyloxycarbonylaminoethyl and 2,2,- for the expermems- 2-trifluoro-l-butyloxycarbonylaminoethyl; and

The resuts are as (mowsi X is selected from the group consisting of NH OH, O-(lower)alkyl, O-benzyl and an anchoring bond linked to a solid polystyrene resin represented by one Table ll of the formula Total Dose Increase of LH Release Compound ng/rat over Control LRF 10 250% Example 3 l0 5000% Example 3 100 5900% Example 3 1000 13,000%

and

Thus, the compound of Example 3 at 10 ng/rat is 5 times more active than LRF.

The compounds of formula I can be administered to mammals intravenously, subcutaneously, intramuscularly or orally for increasing and regulating ovulation since LH is known to trigger ovulation in mammals 2 [See Schally et al., Am. J. Obstet. Gynecol. pp 423-442, Oct. 1972]. The effective dosage will vary with the form of administration and the particular species of mammal to be treated. A typical dosage is a physilogical saline solution containing a compound of formula I. Oral administration may be in either solid or wherein said polystyrene resin is cross linked through the phenyl group on each second carbon atom of the liquid form alkyl chain of said polystyrene, with the proviso that at What is c'laimed is: least one of R, R R R and R is other than hydrogen.

1. A compound selected from the class consisting of 40 2. A compound according to formula II of claim 1 Arg L Pro Gly NH2 (I) wherein X is NH 3. A compound according to formula ll of claim 1 and wherein R is hydrogen and X is and its non-toxic salts; wherein R is a protecting group for the N 5 N" and N nitrogen atoms of arginine selected from 5 the group consisting of nitro, tosyl, benzyloxycarbony], adamantyloxycarbonyl and tert-butylox 4. A compound according to claim 2 wherein R is carbonyl or R is hydrogen; tosyl, R is 2-chlorobenzyloxycarbonyl, R is 2,6-

R is selected from the group consisting of hydrogen dichlor nzyl, R4 i enzyl and R is toSyl.

and a protecting group for the side h in ami o 5. A compound according to claim 1 which is seb tit m; lected from L-Pyroglutamyl-L-histidyl-L-tryptophyl-L- R is a protecting group for the phenolic hydroxyl seryl-L-tyrosyl-D-lysyl-L-leucyl-L-arginyl-L-prolylgroup of tyrosine selected from the group consistglycinamide and its non-toxic acid addition salts.

ing of tert-butyl, tetrahydropyranyl, trityl, benzyl, 

1. A COMPOUND SELECTED FROM THE CLASS CONSISTING OF L-PGLU-L-HIS-L-TRP-L-SER-L-TYR-D-LYS-L-LEU-L-AG-L-PROGLY-NH2
 2. A compound according to formula II of claim 1 wherein X is NH2.
 3. A compound according to formula II of claim 1 wherein R5 is hydrogen and X is
 4. A compound according to claim 2 wherein R1 is tosyl, R2 is 2-chlorobenzyloxycarbonyl, R3 is 2,6-dichlorobenzyl, R4 is benzyl and R6 is tosyl.
 5. A compound according to claim 1 which is selected from L-Pyroglutamyl-L-histidyl-L-tryptophyl-L-seryl-L-tyrosyl-D-lysyl-L-leucyl-L -arginyl-L-prolyl-glycinamide and its non-toxic acid addition salts. 